A wealth of different standards have been elaborated, in part with different aims, for networking devices in the household. One of the systems provides for the devices to be networked on the basis of the “Internet protocol” IP. The system has become known by the abbreviation UPnP, which stands for Universal Plug and Play. A UPnP standard is currently available in version 1.1. More detailed information regarding the UPnP system and the associated standard can be found on the official Internet page of the UPnP consortium.
The UPnP system has no restrictions regarding the device types. This is intended to allow both devices from the consumer electronics field, such as TV, DVD player, set-top box, video recorder, camcorder etc., and also other devices in the household, for example washing machine, chillers, heating control, coffee machines, lighting and shutter control, alarm systems and others, to be networked. Personal computers may likewise be regarded as belonging to the category of consumer electronics devices. These are also covered by the UPnP system and can also be integrated into the network.
However, the UPnP system does not contain a specification for the lower layers of the OSI/ISO reference model for data communication. This concerns particularly the physical layer and the data link layer. The UPnP system therefore no longer contains a specification regarding what transmission medium needs to be used to transmit the data which are to be interchanged. Different transmission standards are permissible in this case. Examples of suitable transmission standards are the Ethernet protocol, the IEEE-1394 protocol, and even wireless transmission based on IEEE 802.11x, Bluetooth or Hiperlan/2 are likewise suitable.
The UPnP specification describes how devices based on the UPnP standard are designed and how they can be controlled. One of the basic ideas of this specification is that it is possible to operate any UPnP device using a standard HTML browser. To this end, every UPnP device has a web server on which it is possible to store the HTML pages for operating the device (the “presentation pages”).
In the UPnP standard, the localization of UPnP devices in the network is the responsibility of “control point devices”. However, this involves the respective UPnP devices themselves registering with the control point devices. Equally, control point devices can look for UPnP devices in the network.
When a control point device has found a UPnP device, it fetches the device's description from the URL (Uniform Resource Locator) indicated during registration using the HTTP and TCP-IP protocols. The UPnP device provides the description in the form of an XML document. Using the information which the control point has obtained from the device's description document, this device can now send “SOAP messages” (Simple Object Access Protocol) to the device's control URL in order to control said device.